Moth brawl: A little moth is causing big problems in Cruso
The presence of a devastating invasive moth has been detected in Haywood County.
Wikipedia photo
Last week, more than a hundred people turned up to an informational meeting about a North Carolina Department of Agriculture plan to treat a small portion of Haywood County’s Cruso community for an invasive species of moth. And they weren’t happy.
Voicing legitimate concerns over private property rights and the inability to opt out of the aerial spray treatment, some in the audience also contended that the non-toxic treatment is worse than an infestation, which can have serious ecological and economic consequences.
“Without early detection and rapid response, the invasive gypsy (spongy) moth will continue to reproduce and take a stronghold in forested areas,” said Joy Goforth, a plant pest administrator with the NCDA. “Spongy moth infestations alter the ecology of an area by reducing habitat, increasing erosion and other factors. In addition, establishment of this pest will have grave impact financially on the local forestry and nursery industries and can impact tourism and property values.”
First described by Swedish taxonomist Carl Linnaeus in 1758, the moth’s Latin name, lymantria dispar, means “unequal destroyer.” Unequal refers to the size difference between males and females, and destroyer alludes to its devastating effect on more than 300 species of plants and trees.
Known for centuries as the gypsy moth, the little creature has recently undergone a name change to spongy moth — its previous moniker is now considered insulting to members of the Romani culture.
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A Medford, Massachusetts, man imported the European pest to the U.S. in 1869, hoping to establishing a new industry by interbreeding them with silkworms.
Predictably, some escaped, and the species has slowly wreaked havoc on hundreds of millions of acres of land during a steady southwesterly spread from eastern Massachusetts through all of New England on down to West Virginia and Virginia, along with Wisconsin and Michigan in the Great Lakes region.
Since 1970, the spongy moth has deforested more than 75 million acres, including at least 2.25 million acres in 2017 alone, according to Goforth.
Goforth led the March 21 meeting at the Historic Haywood County Courthouse, along with officials from the U.S. Forest Service who explained that Western North Carolina is on the frontlines of the infestation, which has crept into North Carolina along the coastal border with Virginia in the east and on into the Asheville area in the west.
The moths can extend their range by as much as 13 miles a year.
Female spongy moths are flightless. They attract mates by releasing a pheromone that helps males detect their location. Once that happens, the females lay an egg mass, usually in trees. The egg mass can produce anywhere from 100 to 1,000 caterpillars.
One caterpillar can eat 1 square-foot of foliage per day, and they especially like oaks, which are plentiful in most of Southern Appalachia.
When they emerge from the egg mass en masse, the caterpillars can swarm, leaving behind prolific amounts of feces and endangering people and pets with the hairs on their backs, which are an irritant.
Regular defoliation injures trees, which then become susceptible to disease. Once spongy moth populations take hold, they can impact the forestry industry, nursery stock and the tourism economy. The loss of large trees also contributes to erosion, which can impact water quality.
Around mid-June, the caterpillars enter the pupal stage, emerging from cocoons two weeks later. Adult moths grow to about an inch in size, do not eat, and live for about a week.
The NCDA began to take note of the problem in Haywood County around 2019, through a trapping program meant to assess both the existence and the size of local populations.
Traps laced with the female pheromone attract males, if there are any around. North Carolina has monitored the moths since 1980, deploying roughly 18,000 traps across the state each year.
Contrary to statements by some members of the public at the meeting, the traps don’t invite an infestation, because the pheromones are only effective within a 50-meter radius.
If more than three male moths are captured in any trap, that’s a red flag, according to Tom Coleman, an entomologist with the U.S. Forest Service who was present at the meeting and helped Goforth answer questions posed by the public. If a series of traps all contain more than three moths, it’s downright alarming.
One trap in Cruso caught five; four traps within the 2,297-acre (3.6 square miles) study area had three or more, and an additional six traps each captured one.
Relentless, the spongy moths are eventually expected to overtake all of Western North Carolina by 2045, but a number of treatments are available to help slow the spread.
Some are bacterium based, some are viruses and some are straight-up poisons that create unintended impacts on other animals, insects and the environment, but the treatment chosen for Cruso takes advantage of a little trickery in regard to the critical role of the female pheromone in breeding.
It’s called SPLAT-GMO (Specialized Pheromone and Lure Application Technology). The “GMO” acronym does not stand for “genetically modified organism” as with some food products, but rather for “Gypsy Moth.”
It consists of 87% inert food grade ingredients, mainly oils, wax, emulsifiers and water. The other 13% is a chemical formulation of the female’s pheromone.
The way it works is by confusing males who pinpoint the location of females through their natural release of the pheromone.
When the treatment is sprayed on tree canopies, it’s suddenly everywhere, making it difficult for males to find females with which to breed. It’s basically the equivalent of trying to spot a single candle amid a raging forest fire.
The treatment doesn’t actually kill the moths. It simply reduces their chances of successful breeding.
“If you ask anyone who works in our industry, this is touted as one of if not the most successful treatment programs,” Coleman said.
Manual trapping of the moths remains an option, but it’s far from guaranteed to slow the spread and it’s economically unfeasible. Coleman said that in the Cruso area, manual trapping would require nine traps per acre. Trapping a block this size would cost roughly $500,000.
The SPLAT-GMO treatment is safe, Coleman said, and the existence of male moths in the spray grid proves that the active ingredient in the treatment, the female pheromone, is already in the environment there.
Coleman explained that the SPLAT-GMO program is more than 20 years old and has been used to treat about 300,000 acres a year in the U.S. from the Outer Banks of North Carolina to the Canadian border. Coleman said he wasn’t aware of any reports of hospitalization from the treatment, but was aware of health concerns from the caterpillars — especially from their hairs.
Spraying of a diluted concentration of the SPLAT-GMO treatment will begin in late June, just as the moths begin to emerge from their cocoons, intent on breeding.
Crop dusters will wait for the exact moment that weather conditions, including winds and temperature, make the spraying as effective as possible.
Not all of the 2,297 acres will be sprayed — only areas with trees. Pilots will shut off their spray valves over open farmland and bodies of water, including creeks, and carefully monitor spray drift.
Although it’s non-toxic to humans, pets, fish or other insects, residents should avoid direct exposure and bring animals inside. If overspray lands on produce, or on vehicles, a simple wash with detergent should be applied.
Property owners will receive a mailer with a “spray window,” because the precise time won’t be known until it occurs. Once that happens, most of the spray will remain in tree canopies. The treatment will be sprayed in straight lines at 100-foot intervals, and the whole thing will take less than three hours.
Within three hours after application, the product becomes rain-fast and UV resistant. Drip isn’t really a concern, Coleman said.
At least one property owner asked Goforth if it was possible to opt out of the spray treatment. Goforth said it wasn’t, because the NCDA is empowered by statute in the North Carolina Plant Pest law to detect, suppress and eradicate “any insect, mite, nematode, other invertebrate animal, disease, noxious weed, plant or animal parasite in any stage of development which is injurious to plants and plant products.”
In fact, it’s actually a crime for any person to “knowingly and willfully keep upon his premises any plant or plant product infested or infected by any dangerous plant pest, or permit dangerous plants or plant parasites to mature seed or otherwise multiply upon his land,” per NCGS 36C-4-421.
Ultimately, the treatment regimens — performed more than 100 times in the state since 1980 — are at the discretion of the N.C. Commissioner of Agriculture, Steve Troxler, who with a board oversees the N.C. Department of Agriculture.
Goforth said that in the coming weeks, NCDA will set a date for another public information session on the treatment.
“North Carolina is defined in many ways by its lush tree canopy and green natural resources,” Goforth said. “Through the Slow the Spread efforts, including targeted treatments where the spongy moth population is on the rise, we hope we can prevent damage to our forests. Western North Carolina won't look like Western North Carolina if we continue to lose trees and tree canopy to pests. And that would be a shame.”
For more information on the invasive spongy moth, visit the U.S. Department of Agriculture website. To ensure notification of the next public information session, contact Joy Goforth, plant pest administrator, at This email address is being protected from spambots. You need JavaScript enabled to view it..
